As shown in FIG. 1, a zipper head 10 of the prior art consists of a head 12, a pull tab 13 fastened at one end thereof with the head 12, and a pull member 14 fastened at one end thereof with another end of the pull tab 13 to facilitate the pulling of the head 12. The pull member 14 has a retaining ring 15, whereas the pull tab 13 has a retaining hook 16, which is engaged with the retaining ring 15. Such a prior art zipper head 10 as described above is defective in design in that the retaining hook 16 is relatively small and can not be easily made by a molding tool, thereby resulting in a relatively high rejection rate.
As shown in FIGS. 2 and 3, another prior art zipper head 20 consists of a head 20, and a pull tab 23 having a hooked portion 24. Located between the hooked portion 24 and a cross beam 25 of the pull tab 23 is an insertion slot 26, as shown in FIG. 3. The insertion slot 26 is intended to locate an arm 271 of a U-shaped elastic piece 27 such that the curved portion 273 is connected with the cross beam 25, and that another arm 272 of the elastic piece 27 serves to close the opening of the hooked portion 24. This prior art zipper head 20 is defective in design in that the elastic piece 27 is not located securely and is thus vulnerable to falling out of the slot 26. To overcome such a deficiency as described above, the cross beam 25 is provided with two protruded portions 28, as shown in FIG. 2, for riveting the curved portion 273 of the elastic piece 27. The addition of the two protruded portions 28 is responsible for an increase in the cost of making the zipper head 20 without improving the quality of the zipper head 20. In addition, the elastic piece 27 can not be held securely by riveting in view of the fact that the two protruded portions 28 are relatively small and can not be securely riveted. In other words, the addition of the two protruded portions 28 complicates the process of making the zipper head 20 without resulting in a meaningful improvement in the quality of the zipper head 20.